In this book NYT science writer Nicholas Wade advances two simple premises: firstly, that we should stop looking only toward culture as a determinant of differences between populations and individuals, and secondly, that those who claim that race is only a social construct are ignoring increasingly important findings from modern genetics and science. The guiding thread throughout the book is that "human evolution is recent, copious and regional" and that this has led to the genesis of distinct differences and classifications between human groups. What we do with this evidence should always be up for social debate, but the evidence itself cannot be ignored.

That is basically the gist of the book. It's worth noting at the outset that at no point does Wade downplay the effects of culture and environment in dictating social, cognitive or behavioral differences - in fact he mentions culture as an important factor at least ten times by my count - but all he is saying is that, based on a variety of scientific studies enabled by the explosive recent growth of genomics and sequencing, we need to now recognize a strong genetic component to these differences.

The book can be roughly divided into three parts. The first part details the many horrific and unseemly uses that the concept of race has been put to by loathsome racists and elitists ranging from Social Darwinists to National Socialists. Wade reminds us that while these perpetrators had a fundamentally misguided, crackpot definition of race, that does not mean race does not exist in a modern incarnation. This part also clearly serves to delineate the difference between a scientific fact and what we as human beings decide to do with it, and it tells us that an idea should not be taboo just because murderous tyrants might have warped its definition and used it to enslave and decimate their fellow humans.

The second part of the book is really the meat of the story and Wade is on relatively firm ground here. He details a variety of studies based on tools like tandem DNA repeats and single nucleotide polymorphisms (SNPs) that point to very distinctive genetic differences between populations dictating both physical and mental traits. Many of the genes responsible for these differences have been subject to selection in the last five thousand years or so, refuting the belief that humans have somehow "stopped evolving" since they settled down into agricultural communities. For me the most striking evidence that something called race is real comes from the fact that when you ask computer algorithms to cluster genes based on differences and similarities in an unbiased manner, these statistical programs consistently settle on the five continental races as genetically distinct groups - Caucasian, East Asian, African, Native American and Australian Aboriginal. Very few people would deny that there are clear genetic underpinnings behind traits like skin color or height among people on different continents, but Wade's achievement here is to clearly explain how it's not just one or two genes underlying such traits but a combination of genes - the effects of many of which are not obvious - that distinguish between races. The other point that he drives home is that even minor differences between gene frequencies can lead to significant phenotypic dissimilarities because of additive effects, so boiling down these differences to percentages and then interpreting these numbers can be quite misleading.

Wade also demolishes the beliefs of many leading thinkers who would rather have differences defined almost entirely by culture - these include Stephen Jay Gould who thought that humans evolved very little in the last ten thousand years (as Wade points out, about 14% of the genome has been under active selection since modern humans appeared on the scene), and Richard Lewontin who perpetuated a well-known belief that the dominance of intra as opposed to inter individual differences makes any discussion of race meaningless. As Wade demonstrates through citations of solid research, this belief is simply erroneous since even small differences between populations can translate to large differences in physical, mental and social features depending on what alleles are involved; Lewontin and his followers' frequent plea that inter-group differences are "only 15%" thus ends up essentially translating to obfuscation through numbers. Jared Diamond's writings are also carefully scrutinized and criticized; Diamond's contention that the presence of the very recently evolved gene for malaria resistance can somehow be advanced as a dubious argument for race is at best simplistic and at worst a straw man. The main point is that just because there can be more than one method to define race, or because definitions of race seem to fray at their edges, does not mean that race is non-existent and there is no good way to parse it.

The last part of the book is likely to be regarded as more controversial because it deals mainly with effects of genetics on cognitive, social and personality traits and is much more speculative. However Wade fully realizes this and also believes that "there is nothing wrong with speculation, of course, as long as its premises are made clear", and this statement could be part of a scientist's credo. The crux of the matter is to logically ask why genes would also not account for mental and social differences between races if they do account for physical differences. The problem there is that although the hypothesis is valid, the evidence is slim for now. Some of the topics that Wade deals with in this third part are thus admittedly hazy in terms of corroboration. For instance there is ample contemplation about whether a set of behavioral and genetic factors might have made the West progress faster than the East and inculcated its citizens with traits conducive to material success. However Wade also makes it clear that "progressive" does not mean "superior"; what he is rather doing is sifting through the evidence and asking if some of it might account for these more complex differences in social systems. Similarly, while there are pronounced racial differences in IQ, one must recognize the limitations of IQ, but more importantly should recognize that IQ says nothing about whether one human is "better" or "worse" than another; in fact the question is meaningless.

Wade brings a similar approach to exploring genetic influences on cognitive abilities and personality traits; evidently, as he recognizes, the evidence on this topic is just emerging and therefore not definitive. He looks at the effects of genes on attributes as diverse as language, reciprocity and propensity to dole out punishment. This discussion makes it clear that we are just getting started and there are many horizons that will be uncovered in the near future; for instance, tantalizing hints of links between genes for certain enzymes and aggressive or amiable behavior are just emerging. Some of the other paradigms Wade writes about, such as the high intelligence of Ashkenazi Jews, the gene-driven contrast between chimp and human societies and the rise of the West are interesting but have been covered by authors like Steven Pinker, Greg Cochran and Gregory Clark. If I have a criticism of the book it is that in his efforts to cover extensive ground, Wade sometimes gives short shrift to research on interesting topics like oxytocin and hormonal influences. But what he does make clear is that the research opportunities in the field are definitely exciting, and scientists should not have to tiptoe around these topics for political reasons.

Overall I found this book extremely well-researched, thoughtfully written and objectively argued. Wade draws on several sources, including the peer reviewed literature and work by other thinkers and scientists. The many researchers whose work Wade cites makes the writing authoritative; on the other hand, where speculation is warranted or noted he usually explicitly points it out as such. Some of these speculations such as the effects of genetics on the behavior of entire societies are quite far flung but I don't see any reason why, based on what we do know about the spread of genes among groups, they should be dismissed out of hand. At the very least they serve as reasonable hypotheses to be pondered, thrashed out and tested. Science is about ideas, not answers.

But the real lesson of the book should not be lost on us: A scientific topic cannot be declared off limits or whitewashed because its findings can be socially or politically controversial; as Wade notes, "Whether or not a thesis might be politically incendiary should have no bearing on the estimate of its scientific validity." He gives nuclear physics as a good analogy; knowledge of the atom can lead to both destruction and advancement, but without this knowledge there will still be destruction. More importantly, one cannot hide the fruits of science; how they are used as instruments of social or political policy is a matter of principle and should be decoupled from the science itself. In fact, knowing the facts provides us with a clear basis for making progressive decisions and gives us a powerful weapon for defeating the nefarious goals of demagogues who would use pseudoscience to support their dubious claims. In that sense, I agree with Wade that even if genetic differences between races become enshrined into scientific fact, it does not mean at all that we will immediately descend into 19th-century racism; our moral compass has already decided the direction of that particular current.

Ultimately Wade's argument is about the transparency of knowledge. He admonishes some of the critics - especially some liberal academics and the American Anthropological Association - for espousing a "culture only" philosophy that is increasingly at odds with scientific facts and designed mainly for political correctness and a straitjacketed worldview. I don't think liberal academics are the only ones guilty of this attitude but some of them certainly embrace it. Liberal academics, however, have also always prided themselves on being objective examiners of the scientific truth. Wade rightly says that they should join hands with all of us in bringing that same critical and honest attitude to examining the recent evidence about race and genetics. Whatever it reveals, we can be sure that as human beings we will try our best not to let it harm the cause of our fellow beings. After all we are, all of us, human beings first and scientists second.

A modified version of this review was first published on Amazon.com.

Update: My fellow Sci Am blogger Eric Michael Johnson has a characteristically thoughtful and well-written review of the book. I happen to disagree with Eric on the value of the book - and think that on one important level the debate is about the value of speculation in science - but I appreciate his take on it. It's also a pity - although hardly surprising - that unabashed racists, white supremacists and creationists are using the book to support their ideas. Not the first time that a controversial work was hijacked by people on the extremist fringe. This would also be an appropriate time to point out that any comment catering to this fringe will be immediately deleted and the commenter banned.

The views expressed are those of the author and are not necessarily those of Scientific American.

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